Device for injection molding silicone rubber

ABSTRACT

A precision cassette plate, which is an integral component of a mold assembly in an injection molding system, is designed to secure a predetermined number of components fabricated in an injection molding process. The precision cassette plate is designed with two pre-alignment holes and two precision position anti-rotational features that guarantee accurate placement of the precision cassette plate each time at each stage of the manufacturing/assembly process.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to devices and methods for manufacturingmedical devices, and more particularly to a mold assembly comprisingprecision cassette plates for use in a small scale, self-contained,fully enclosed, filtered manufacturing cell that molds and distributesmicro-sized components, for example, drug delivery devices or portionsthereof for use in the eye.

2. Discussion of the Related Art

The corner of each eye is called a canthus, with the nose side calledthe nasal canthus and the ear or temporal side called the temporalcanthus. At the lower and upper eyelid margins of the nasal canthus aresmall openings called puncti or puncta. As used herein, both puncti andpuncta shall be understood to be the plural form of punctum. Eachpunctum drains tears from the eyes. A punctal plug or occluder is anophthalmic device for insertion into a punctum of an eye in order totreat one or more disease states. Typically, a punctal plug ispositioned to block tear drainage thereby helping treat dry eyes.Punctal plugs may also be utilized for sustained release of medicationto the eye for the treatment of a wide variety of ocular diseases.

In order to treat infection, inflammation, glaucoma, and other oculardiseases, drugs are often required to be administered to the eye. Aconventional method of drug delivery is by topical application to theeye's surface. The eye is uniquely suited to this surface route of drugadministration because, properly constituted, drugs can penetratethrough the cornea, rise to therapeutic concentration levels inside theeye, and exert their beneficial effects. In practice, eye dropscurrently account for more than ninety-five (95) percent of drugdelivery methods for the eye. Rarely are drugs for the eye administeredorally or by injection, either because they reach the eye in too low aconcentration to have the desired pharmacological effect, or becausetheir use is complicated by significant systemic side effects.

Eye drops, though effective, are unrefined and inefficient. When an eyedrop is instilled in the eye, it typically overfills the conjuctivalsac, the pocket between the eye and the eyelids, causing a substantialportion of the drop to be lost due to overflow of the eyelid margin ontothe cheek. In addition, a substantial portion of the drop remaining onthe ocular surface is washed away by tears into the tear drainagesystem, thereby diluting the concentration of the drug. Not only is thisshare of the drug dose lost before it can cross the cornea, but thisexcess drug may be carried into the nose and throat where it is absorbedinto the general circulation, sometimes leading to serious systemic sideeffects. The small portion of the drug in the eye drop which doespenetrate the cornea results in an initial peak tissue concentration, ahigher level than is required for the initial pharmacological effect.This tissue concentration then gradually decreases, such that by thetime the next eye drop is due, the tissue concentration and the intendedpharmacological effect may be too low.

To compound the problems described above, patients often do not usetheir eye drops as prescribed. Often, this poor compliance is due to aninitial stinging or burning sensation caused by the eye drop. Certainly,instilling eye drops in one's own eye can be difficult, in part becauseof the normal reflex to protect the eye. Older patients may haveadditional problems instilling drops due to arthritis, unsteadiness, anddecreased vision, and pediatric and psychiatric patient populations posedifficulties as well. Accordingly, punctal plugs provide a viable meansfor solving the problems of reliable and efficient drug delivery to theeye.

Punctal plugs may be of the temporary variety or of the permanentvariety. Temporary punctal plugs are usually fabricated from collagen orother similar material and are dissolvable. Temporary punctal plugs maybe utilized for short duration treatment or to gauge how an individualwill react to having the insert placed, for example, will the devicecause excessive tearing. Permanent punctal plugs are for long term useand are removable at any time. Permanent punctal plugs are available invarious sizes with the largest size that fits providing maximumeffectiveness. Permanent punctal plugs are typically made of silicone.

A punctal plug typically includes a body portion sized to pass through alacrimal punctum and be positioned within a lacrimal canaliculus of theeyelid.

The punctal plug also comprises a collarette connected to the bodyportion and sized to rest on the exterior of the lacrimal punctum. Theterm lacrimal punctum and lacrimal canaliculus are often utilizedinterchangeably; however, as used herein, the punctum means the openingand the canaliculus is the passageway or duct-like pathways that lead tothe lacrimal sac. If the punctal plug is used to deliver therapeuticagents to the eye, then the body portion may comprise a reservoir forholding the therapeutic agents and the collarette may comprise anopening in communication with the reservoir through which thetherapeutic agents are released.

Punctal plugs are small. For example, punctal plugs may be in the rangeof 0.2 to 0.4 millimeters in diameter and up to 2.0 millimeters inlength. Devices so small are inherently more difficult to manufacturethan larger devices. More importantly, manufacturing small devices in arepeatable and reliable manner is even more difficult. In addition,handling these small devices for further processing while maintainingtheir orientation for accountability is also important. Accordingly,there exists a need for a micro mold and technology for producing ormanufacturing punctal plugs with greater efficiency, even higher qualityand higher repeatability than currently utilized technologies. Therealso exists a need for simplifying the overall size and complexity ofthe mold and molding process.

SUMMARY OF THE INVENTION

The mold assembly comprising a precision cassette plate of the presentinvention overcomes the limitations associated with the prior art asbriefly described above.

In accordance with one aspect, the present invention is directed to amold assembly for an injection molding system. The mold assemblycomprising a top portion, the top portion including one or more cassettealignment pins extending therefrom, a precision cassette plate, thecassette plate including one or more openings in which parts arefabricated and secured, one or more pre-alignment through-holes whichengage the one or more cassette alignment pins, and two anti-rotationalfeatures, a runner/gate insert element, the runner/gate insert elementincluding a sprue channel and one or more runners and gates, the numberof runners and gates equals the number of openings in the precisioncassette plate, and a base portion, including an opening through which anozzle of an injection molding system is positioned and makes contactwith the sprue channel of the runner/gate inset element.

In accordance with another aspect, the present invention is directed toa method for molding parts. The method comprising introducing a materialinto a sprue/runner/gate arrangement in a mold assembly having aprecision cassette plate with one or more openings for the fabrication,alignment and securement of the molded parts, removing the precisioncassette plate from the mold assembly and separating the molded partsfrom the sprue/runner/gate with the molded parts retained therein in apredetermined orientation, and transferring the precision cassette platewith the parts therein for downstream processing while maintaining thesame predetermined orientation.

In accordance with yet another aspect, the present invention is directedto a method for filling cavities in small molded parts. The methodcomprising introducing a material into a sprue/runner/gate arrangementin a mold assembly having a precision cassette plate with one or moreopenings for the fabrication, alignment and securement of the moldedparts, the precision cassette plate including feature for forming acavity in the molded parts, removing the precision cassette plate fromthe mold assembly and separating the molded parts from thesprue/runner/gate with the molded parts retained therein in apredetermined orientation, filling the cavity in each molded part with apredetermine material, and transferring the precision cassette platewith the molded parts and filled cavities therein for downstreamprocessing while maintaining the same predetermined orientation.

The present invention is directed to precision cassette plates forsecuring a predetermined number of molded parts, for example, punctalplugs. The cassette plates are part of the molds utilized in combinationwith a micro silicone mold mounted plunger injection unit which in turnis part of a small scale, self-contained, fully enclosed, filteredmanufacturing cell that molds and distributes micro-sized components,for example, punctal plugs, throughout a complete assembly process. Anexemplary cell comprises an injection molding unit, a mold stand and/orbase, a mold, a cassette pre-heating station and a robotic manipulatormounted within a case having a filtration unit for maintaining asubstantially particle free environment within the case.

The injection molding unit may be configured as a cold deck system or ahot runner system, and may comprise three main components; namely, asilicone cartridge assembly, a micro plunger injection assembly and acold deck nozzle assembly all directly interconnected with one another.The micro silicone mold mounted plunger system reduces the flow path ofsilicone such that part quality and reproducibility is increased whilewaste is reduced. In this exemplary system, the injection unit isincorporated into the silicone mold extremely close to the cold shut-offnozzle. The system has a greatly reduced material flow channel diameterwhich is held constant up to the point of exiting the cold nozzleorifice. This provides a stable pressure constant within the systemunlike that of a reciprocating screw system that begins with a largerdiameter material channel and then reduces over the length of the flowpath of the system. The actual injection stroke end position is locatedat the junction of the material flow channel and the cold shut-offnozzle. This arrangement and reduced material channel volumesignificantly reduces material compression and process variation in theflow of the material, thereby providing superior shot to shotrepeatability.

In a typical injection molding system, the nozzle of the injection unitinjects the molten or liquid material, for example, silicone,thermoplastic resin or metal, into a mold or die. A sprue is a channelthrough which the molten or liquid material is injected out from thenozzle of the injection unit and into the mold. The sprue generally hasa smooth, round, tapered configuration that facilitates smooth materialflow therethrough. Runners are channels through which the moltenmaterial flows from the sprue and into the cavities of the mold viagates. A gate is an entrance through which the molten material entersthe cavity. The gate performs a number of functions, includingrestricting the flow and direction of molten material and facilitatingremoval of the parts from the runners.

The precision cassette is an integral part of the mold assemblyconfiguration and the material handling process. With thisconfiguration, the overall size and complexity of the mold, moldingprocess, and/or overall manufacturing process may be simplified. Thecassette provides for shorter runner lengths which in turn allow forbetter control over pressure variations and temperature variations. Inaddition, the cassette allows parts to be transferred to and through theprocess without a secondary cutting operation. In other words,everything maintains its orientation until the time of part separation.In addition, the precision cassette plate is designed with twopre-alignment holes and two precision positive anti-rotational featuresthat guarantee accurate placement of the cassette each time at eachstage of the manufacturing process.

The present invention is directed to a mold component; namely aprecision cassette that may be moved around anywhere in the moldingprocess while maintaining the orientation of the molded parts orcomponents. In addition, the precision cassette with the parts securedtherein may also be utilized in further processing and/or manufacturingsteps. For example, the precision cassette may be utilized to secure themolded parts or components for coating and/or filling. In other words,the precision cassette may be utilized to secure and align parts fordrug and/or therapeutic agent filling to create a drug delivery medicaldevice such as a punctal plug. With this precision cassette, there is noneed to remove the molded parts or components to a secondary device forpost molding processing. The drug filling may comprise any suitableprocess for adding a therapeutic agent to molded device. The therapeuticagent may be in any form, including dry, liquid, and fiber.

The precision cassette may be utilized under any number processingconditions, including large temperature ranges, large pressure rangesand large humidity ranges. The precision cassette may comprise anysuitable shape and profile as well as include any number of additionalfeatures, all depending on the application. The precision cassette maybe constructed from any number of suitable materials, once againdepending on the application. In addition, although described withrespect to an injection molding process, the precision cassette may beutilized in other types of molding processes, including compressionmolding, transfer molding and casting under vacuum. Also any suitablematerials may be molded in the precision cassette. For example,silicone, thermoplastic resins and metallic materials may be molded inthe precision cassette.

BRIEF DESCRIPTION OF THE DRAWINGS

The foregoing and other features and advantages of the invention will beapparent from the following, more particular description of preferredembodiments of the invention, as illustrated in the accompanyingdrawings.

FIG. 1 illustrates the anatomy of the lacrimal drainage system of thehuman eye.

FIG. 2 illustrates an example of a conventional punctal plug that isknown in the art.

FIG. 3 illustrates an example of a punctal plug, including a reservoirfor the release of one or more therapeutic agents that is known in theart.

FIG. 4A is a diagrammatic representation of an exemplary micro siliconemold mounted plunger injection unit in accordance with the presentinvention.

FIG. 4B is a sectional view of the exemplary micro silicone mold mountedplunger injection unit illustrated in FIG. 4A taken along section lineA-A.

FIG. 4C is a rotated view of the exemplary micro silicone mold mountedplunger injection unit illustrated in FIG. 4A.

FIG. 5 is a diagrammatic representation of a cold deck nozzle assemblyin accordance with the present invention.

FIG. 6 is a diagrammatic representation of a genericsprue/runner/gate/component configuration.

FIGS. 7A and 7B are diagrammatic representations, in two views, of anexemplary cell in accordance with the present invention.

FIG. 8 is a diagrammatic representation of an exemplary cassette inaccordance with the present invention.

FIG. 9 is an exploded diagrammatic representation of an exemplary moldassembly configuration in accordance with the present invention.

FIG. 10 is a detailed diagrammatic representation of a single runner,gate and attached part in accordance with the present invention.

FIGS. 11A and 11B are diagrammatic representations of an exemplarycassette with a part therein in accordance with the present invention.

FIG. 12 is a detailed diagrammatic representation of an exemplarycassette with the part connected to a sprue and runner in accordancewith the present invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

FIG. 1 illustrates the anatomy of the drainage system of a human eye100. Tears are produced by the lacrimal gland, not illustrated, superiorto the outer portion of each eye 100. Tears flow across the surface ofthe eye 100 to a shallow pool, termed the lacrimal lake 102, locatedwhere the upper and lower eyelids come together at their inner ends ornasal ends. From there, the tears drain through small openings in eachof the eyelids, namely, the upper lacrimal punctum 104 and the lowerlacrimal punctum 106. From the upper lacrimal punctum 104 and the lowerlacrimal punctum 106, the tears pass into the upper lacrimal canaliculus108 and lower lacrimal canaliculus 110, respectively, which areduct-like pathways leading to the lacrimal sac 112. The lacrimal sac 112is the superior, expanded portion of the nasolacrimal duct, notillustrated, which drains tears into the nasal system. The upperlacrimal punctum 104 and associated canaliculus 108 typically only drainabout ten percent of the tears from the eye 100, such that theirobstruction virtually never leads to the tear overflow.

Tears or the tear film comprises three layers. The first layer or bottomlayer is the layer that coats the eye and comprises mucin which iscreated by cells in the conjunctiva referred to as goblet cells. Themucin fills in microscopic irregularities on or in the eye's surfacewhich is important to clear vision. The second layer or middle layer ofthe tear film comprises essentially water and makes up the bulk of thetear film. A majority of the watery component is produced or suppliedfrom the main lacrimal or tear gland. Emotional tears and reflect tears,i.e. tears resulting from a stimulus such as bright light or a foreignbody, come from the main lacrimal gland. Accessory lacrimal glands,known as the glands of Wolfing and Kraus are found in the eyelid tissueand also contribute to the watery component. The third or top layer ofthe tear film comprises a thin layer of oil secreted by the meibomianglands and functions to prevent the tears from evaporating too quickly.

Insufficient tears or “dry eye” is a common condition caused byinsufficient production of tears from the lacrimal gland which causessymptoms such as dryness, redness, burning, reflex tearing, itching, orforeign body sensation. In especially difficult cases of dry eye, apunctal occluder or punctal plug may be placed into one or both of thelacrimal puncta 104, 106, see FIG. 1. Punctal plugs prevent the tears,which are being produced in deficient volume by the lacrimal glad, fromdraining into the lacrimal canaliculi 108, 110. Punctal plugs may besecured in the lacrimal puncta without anesthesia and removed with easewhen required.

Referring now to FIG. 2, there is illustrated an exemplary punctal plug200. The punctal occluder or plug 200 comprises a collarette 202 whichis configured to rest on the exterior of the punctum 104, 106 (FIG. 1),a bulb 204 that blockingly projects into the canaliculus 108, 110 (FIG.1), and a body portion 206 connecting the collarette 202 and the bulb204. Commercially available punctal plugs usually have a length ofapproximately 2.0 millimeters, and differ from each other only slightlyin configuration. For example, the bulbs of the punctal plugs aredesigned to prevent the plug from being easily dislodged from thecanaliculus, and may be tapered for ease of insertion into the puncta.The collerette is designed to have a diameter sufficient to prevent theplug from completely entering the canaliculus, and are preferably smoothto minimize irritation of the eye. The body portions of differentpunctal plugs are also similar in design and are essentially anon-functional connection between the collarette and the bulb portions.The collarette 202 may include an aperture 208, illustrated in phantom,extending into the body portion 206 to aid in grasping or securing thepunctal plug 200 during its insertion into the puncta. Examples ofpunctal plugs may be found in U.S. Pat. Nos. 3,949,750 and 5,283,063 toFreeman, U.S. Pat. Nos. 5,053,030, 5,171,270 and 5,723,005 to Herrick,U.S. Pat. No. 5,417,651 to Guena et al., and U.S. Pat. No. 5,423,777 toTajiri et al.

In addition to, or alternately, a punctal occluder or plug may beutilized to deliver one or more therapeutic agents and/or medications.FIG. 3 illustrates an ophthalmic insert or punctal plug 300 that adaptsthe form of a conventional punctal plug 200, as illustrated in FIG. 2,to incorporate a reservoir 310, illustrated in phantom, designed tostore and release medication onto the surface of the eye. The reservoir310 may be configured to release the medication in any number of ways,including pulsatile and continuous. In addition, the reservoir may berefilled as required. As in the previously described exemplaryembodiment, the ophthalmic insert or punctal plug 300 comprises acollarette 302, a bulb 304 and a body portion 306. The punctal plug 300may be molded or otherwise formed from a flexible material, such assilicone, that is impermeable to the medication which will fill thereservoir 310. Although silicone is described herein, it is important tonote that any suitable biocompatible material may be utilized. Thereservoir 310 may be formed by a channel through the interior of thebody portion 306 of the plug 300. In one exemplary embodiment, the bodyportion 306 may be flexible or even accordion shape so as to provide thecapability of lengthwise expansion as it is filled with medication. Thecollarette 302 anchors the plug 300 to the exterior of the lacrimalpunctum 104 and 106 (see FIG. 1) and may be provided with an opening 308which is in fluid communication with the reservoir 310. In order tocontrol the delivery of a specific medication, the geometry of theopening 308 may be customized in a variety of ways. For example, theopening 308 may be designed for releasing the medication at a constantsustained release rate, a pulsatile release rate, an exponential releaserate and/or any combination thereof. Through opening 308, medication isreleased from the reservoir 310 into the tears of the lacrimal lakewhere the medication mixes, as eye drops do, with the tears andpenetrate the eye to have the intended pharmacological and therapeuticeffect. Although not required, the punctal plug 300 may comprise anenlarged bulb 304 to help secure the plug 300 in position within thecanaliculus and also to provide additional volume for the reservoir asillustrated. An example of this type of punctal plug may be found inU.S. Pat. No. 6,196,993 to Cohan et al.

Punctal plugs may take on any number of configurations, sizes and beformed from any number of materials, depending on the desiredfunctionality and/or medications to be delivered.

As set forth above, punctal plugs may take any size and shape.Typically, the body of the punctal plug is in the shape of an elongatedcylinder, and may vary in length in the range from about 0.8 mm to about5 mm and may vary in width in the range from about 0.2 mm to about 3 mm.The size of the opening for medication or drug release may be in therange from about 1 nm to about 2.5 mm. Rather than one large opening atany one location, multiple small openings may be used. The body of thepunctal plug may be wholly or partially transparent or opaque.Optionally, the body may include a tint or pigment that makes the plugeasier to see when it is placed in a punctum.

Punctal plugs may be fabricated from any number of suitablebiocompatible materials including silicone, silicone blends, siliconeco-polymers, for example, hydrophilic monomers ofpolyhdroxyethlmethacrylate, polyethylene glycol, polyvinylpyrrolidoneand glycerol, and silicone hydrogel polymers, for example, thosedescribed in U.S. Pat. Nos. 5,962,548, 6,020,445, 6,099,852, 6,367,929,and 6,822,016. Other suitable biocompatible materials includepolycarbonate, cyclic olefin copolymer, thermoplastic elastomer,polypropylene, polytetrafluoroethylene, tetrafluoroethene, cyclic olefinpolymer, polyurethane, polymethylmethacrylate, poly(ethylene glycol),poly(ethylene oxide), poly(propylene glycol), poly(vinyl alcohol),poly(hydroxyethylmethacrylate), poly(vinylpyrrolidone), polyacrylic,poly(ethyloxazoline), poly(dimethyl acrylamide), phospholipids, forexample, phosphoryl choline derivatives, polysulfobetains, acrylicesters, polysaccharides and carbohydrates, for example, hyaluronic acid,dextran, hydroxyethyl cellulose, hydroxyl propyl cellulose, gellan gum,guar gum, heparin sulfate, chondroitin sulfate, heparin and alginate,proteins, for example, gelatin, collagen, albumin and ovalbumin,polyamino acids, fluorinated polymers, for example,polytetrafluoroethylene and polyvinylidine fluoride, polypropylene,polyethylene, nylon and ethylene-co-vinylacetate.

The exterior surfaces of the punctal plug may be wholly or partiallycoated with a number of different biocompatible coatings. The coatingmay provide a number of benefits, including lubriciousness to aid ininsertion of the device, muco-adhesiveness to improve tissuecompatibility, texture to aid in anchoring the device and/or anycombination thereof. Suitable biocompatible coatings include gelatin,collagen, hydroxyethyl methacrylate, poly(vinylpyrrolidone),poly(ethylene glycol), heparin, chondroitin sulfate, hyaluronic acid,synthetic and natural proteins, polysaccharides, thiomens, thiolatedderivates of polyacrylic acid and chitosan, polyacrylic acid,carboxymethal cellulose and combinations thereof.

It has been found that with certain therapeutic agents or medications,it may be desirable to create a barrier layer between the therapeuticagent containing material to be released from the reservoir within thepunctal plug and the interior surface of the walls that define thereservoir due to possible interactions, or inadvertent leaching of theactive therapeutic agent through the wall of the punctal plug. Inaddition, it has been found that the retention of therapeutic agentwithin the reservoir may be aided by the selection of the geometricconfiguration of the punctal plug, or with the addition of variousanchoring features. For example, a reservoir may comprise a simplecylindrical configuration which may not securely hold a particulartherapeutic agent within the reservoir. In other words, that shape, evenwith a primer layer or adhesive layer may not be sufficient to hold theagent in place. Accordingly, the geometry of the reservoir may bemodified to include protrusions or indents for holding the agent. Thesegeometric variations may be utilized alone or in combination withvarious barrier layers, adhesives and/or primer layers. In other words,various combinations of geometries and coatings may be utilized to holdthe drug in and/or force the drug out as required. For example, abarrier layer may be disposed on the external surface of the punctalplug to inhibit diffusion of the therapeutic agent in the body of thepunctal plug and to inhibit the infusion of tears into the reservoircontaining the therapeutic agent. In addition, the geometry of thepunctal plug may be modified to create a better fit within thecanaliculus.

Processes for manufacturing the punctal plugs are known in the art.Typically, the punctal plugs are manufactured by injection molding, castmolding, transfer molding, stamping, embossing or the like. Preferably,the reservoir is filled with one or more active agents, with or withoutother materials, subsequent to the manufacture of the device. The amountof active agent as well as other constituents, such as excipients, willdepend on a number of factors, including the active agent or agentsselected the desired release rate, and the melting points of thetherapeutic agent. Preferably, the amount utilized is a therapeuticallyeffective amount meaning an amount effective to achieve the desiredtreatment, inhibiting or prevention effect.

The device and method for injection molding silicone rubber may utilizean automatic, miniature sized silicone molding cell that includes anovel silicone mold and plunger injection unit to produce a drugdelivery device; namely, a punctal occluder or plug with a reservoir. Inaddition to producing punctal plugs, the injection unit may be utilizedto produce components of punctal plugs as well as any extremely smalldevice to be fabricated from a thermoset elastomer such as silicone.

Silicone molding in the medical, electronics, packaging and automotiveindustries is increasing due to a number of factors, including itshardness range (5 to 90 durometer), the fact that it is inert, odorless,tasteless, hypo-allergenic, it is flexible and durable and can becompounded for special properties. However, the injection molding ofsilicone rubbers is different than that of traditional thermoplasticinjection molding. To mold a component with a thermoplastic requiresthat a thermoplastic resin be heated and injected into a cold mold. Tomold a component with a silicone rubber requires that the liquidsilicone rubber be kept cool and then injected into a heated mold. Thedesign and manufacture of a silicone mold is also different from that ofthermoplastic. The cold deck or the cold mold deck, as described in moredetail subsequently, allows for the equal distribution of the siliconerubber to each cavity at the same hydraulic pressure and consistenttemperatures profile.

The injection molding of silicone or liquid silicone rubber is a processutilized to manufacture or produce pliable, durable components in highvolume. Silicone or liquid silicone rubber is a high purity platinumcured silicone having a low compression set, excellent stability andability to resist extreme temperatures, both hot and cold. It is ideallysuited for the production of components or devices where high quality isimportant, for example, in medical devices. Due to the thermosettingnature of the silicone, liquid silicone injection molding requiresspecial treatment, including intensive distributive mixing whileensuring that the silicone remains at a low temperature prior to itbeing injected into a heated cavity or mold and vulcanized.

Chemically, silicone rubber is part of a family of thermoset elastomersthat include a backbone of alternating silicon and oxygen atoms andmethyl or vinyl side groups. Silicone rubber comprises about thirty (30)percent of the silicone family.

The typical liquid silicone injection molding machine or systemcomprises a number of functional components, including injectors,metering units, supply drums, mixers, nozzles, at least one mold clampand mold. The injectors or injection device is responsible forpressuring the liquid silicone to facilitate injection of the siliconeinto the cavities of the mold. Pressure and injection rate may beadjusted automatically and/or manually to achieve various desiredresults. The metering units pump the two primary liquid materials;namely, the base forming silicone and the catalyst, ensuring that thetwo materials maintain a predetermined constant ratio while beingsimultaneously released. Supply drums serve as the primary containersfor the unmixed materials. The supply drums as well as other containers,for example, containers holding pigmentation materials, are connected tothe main pumping section of the system. A static and/or dynamic mixercombines the materials after they exit the metering units. Static mixingis typically utilized with simple mixing ratios and similar viscositiesbetween the components to be mixed, whereas dynamic mixing is typicallyutilized with extreme mixing ratios and large differences between theviscosities of the components to be mixed. Once combined, pressure isused to drive the mixture into an injection unit, through an attachednozzle, and into a designated mold. Typically, the nozzle includes anautomatic and/or manual shut-off value to prevent leakage andoverfilling the mold. The mold clamp secures the mold during theinjection molding process and is used to open the mold once the processis complete.

As briefly described above, the silicone molding of a part or componentrequires that the liquid silicone rubber be kept cool (60 to 77 degreesFahrenheit) prior to being injected into a heated mold (340 to 410degrees Fahrenheit). A runnerless molding system or cold deck is adevice which allows for the equal distribution of material to eachcavity at the same hydraulic pressure and consistent temperatureprofile. The raw materials utilized in the process are mixed in aone-to-one ratio, typically via the static mixer. Once the componentscome into contact, the curing process immediately begins. Accordingly,the cold drive is utilized to retard the curing process prior to thematerial being introduced into the heated mold. Essentially, theone-to-one mixed compound is pumped through the cold deck and then intoa heated cavity where the vulcanization takes place. The cold deck andgeneral cooling results in minimal loss of material as the injectionoccurs directly into the part, cavity or mold. This cooling processallows for the production of liquid silicone rubber parts withsubstantially zero material valve gate waste.

Silicone injection molding of micro sized components, such as punctalplugs or components of punctal plugs, in a conventional siliconeinjection molding machine is difficult due to the imbalance between theamounts of material flow relative to component volume. In other words,the high volume of material within the material flow path inconventional molding equipment is much greater than the volume of themicro sized components thereby eliminating the control system's abilityto discern between filled and non-filled cavities.

The device and method for injection molding silicone rubber may utilizea micro sized, plunger style, silicone injection unit that mountsdirectly into or onto a silicone mold along with a cold deck nozzle. Theexemplary injection unit comprises a single material cartridge thatfeeds pre-mixed silicone directly through a one-way check valve into theplunger unit and the cold shut off nozzle of the cold deck mold.Pressure sensors/transducers mounted within the material flow path, asdescribed in detail subsequently and hard wired into the unit's controlsystem monitor and control the injection sequencing and flow of thematerial through the injection unit. The plunger unit may comprise anelectric motor, a pneumatically driven device or any other suitablemeans that is actuated by signals from the injection unit's controlsystem based upon feedback signals from the sensors/transducers. Theplunger unit works in conjunction with the cold nozzle shut off value toregulate mold cavity filling by pressure sensing rather than screwposition or time like that in a conventional injection machine/process.Accordingly, the injection unit eliminates the need for peripheralmaterial pumping stations, lengthy material feed lines, and aconventional machine injection unit.

Essentially, the exemplary injection unit simplifies the molding processassociated with the micro silicone molding of punctal plugs, punctalplug components and/or any other micro sized devices. Although theexemplary injection unit described herein utilizes silicone, it isimportant to note that the exemplary injection unit may be utilized withany suitable material for punctal plugs that can be injection molded andhas molding properties similar to that of silicone and/or otherthermoset elastomers for the reasons set forth above. Important to theperformance of such a unit is shot to shot repeatability withoutcompromising the mechanical and performance attributes of the punctalplug. The design and construction of the mold tool is critical inenhancing and optimizing part consistency and geometry. The injectionunit provides a simple and eloquent processing solution not based solelyon tool and equipment miniaturization, but on reducing complexity,degrees of freedom and process variation.

Conventional technology uses high volume cavity tooling i.e. high volumeas in a high number of cavities to fill, to compensate for volumecontrol from cycle to cycle. This is done to overcome the large volumeof a metered amount of material coming from theplasticizer/reciprocating module needed to generate some level ofcontrol with material volume and position accuracy. This becomes verydifficult to control with very small shot sizes when one wants tocontrol displacement and shot accuracy (variation increases with moldvariations as explained by the power law). The current technologyprocess flow may be briefly described as follows: In a first step, asilicone cross linker and plasticizer are statically and/or dynamicallymixed in a mixing station. In a second step, the mixture is pumped intoa metering/reciprocating plasticizer through an elaborate network ofhoses from the mixing station. In a third step, the material is meteredand dose determination is made by position and screw rotation. In afourth step, the metered material is injected into a manifold forseparation. In a fifth step, the material in the manifold is dividedinto equal amounts and deposited into the cold mold deck. The cold molddeck allows for the equal distribution of material to each cavity at thesame hydraulic pressure and consistent temperature profile. In a sixthstep, the material in the cold deck is injected into the mold cavity.

A much more simplified version of the injection unit or system comprisesa plunger unit which is attached directly into the cold deck, therebysubstantially shortening the material flow path. The position and shotsize may be accurately controlled utilizing a fine pitch position screwor a dc positional servo drive. The mold cavity is also directly mountedto the nozzle of the cold deck. The process flow in accordance with thepresent invention may be briefly described as follows: In a first step,a mixture, typically 1 to 1, of the silicone is loaded into 0.5 or halfliter cartridges. In a second step, the 0.5 liter cartridge is attacheddirectly to the plunger unit. With this direct attachment arrangement,there is no air contamination from hoses while establishing a shorterflow path. In a third step, the silicone is accuratelypositioned/metered into the cold deck drop. In a final step, thesilicone is injected into the mold cavity. A more detailed descriptionof the process is given subsequently.

The system set forth herein allows for very small shot sizes and moreprecision over the process with reduced variation as compared to theconventional system described above. Direct plunging into the cold deckprovides for more control over material compressibility, pressure, partgeometry and temperature during the high pressure fill and cure cycleand very accurate shot design technology. The control logic sequence ofthe plunger provides for silicone from the cartridge to be delivered byregulator controlled air pressure into the plunger unit through aone-way check valve, then when signaled, the plunger and nozzle valveopen simultaneously and the plunger rod drives the pre-set dose ofsilicone through the feed channel into the mold, and the nozzle valvecloses and the plunger retracts to its shot recharge position. This isaccomplished by regulator controlled air pressure to about 0.8 bar. Theplunger unit comprises a 3 mm diameter plunger with fine stroke positionby screw and digital micrometer or linear encoder. This plunger unit isa stand-alone unit that is easy to repair and overhaul. It is importantto note that while the device as described and illustrated is pneumaticin terms of piston control as well as a number of other features, anysuitable alternate means may be utilized.

Referring to FIGS. 4A, 4B and 4C, there is illustrated an exemplarymicro silicone mold mounted plunger injection unit or system 400 thatmay be utilized with the present invention. FIG. 4B is a cross-sectionalview of the system 400 illustrated in FIG. 4A taken along section lineA-A and FIG. 4C is a rotated view of the system 400 illustrated in FIG.4A. The entire system 400 is configured as a cold deck system andcomprises three main components; namely, a silicone cartridge assembly402, a micro plunger injection assembly 404 and a cold deck nozzleassembly 406.

The silicone cartridge assembly 402 comprises a cylindrical canister 408with at least one threaded connector 410 and a pneumatic connection port412. The silicone cartridge assembly 402 is connected to the cold decknozzle assembly 406 via a simple piping arrangement 414 which includes acheck valve 416. The check valve 416 prevents back pressure from thecompressed material in the system, described in more detail below, fromforcing silicone back into the silicone cartridge assembly 402. Thesilicone cartridge assembly 402 is secured to the micro plungerinjection assembly 404 via bracket 418. A container, not illustrated,comprising a pre-mixed, one-to-one (1:1) silicone mixture is positionedin the cylindrical canister 408 such that pneumatic pressure from port412 forces the silicone mixture through the check valve 416 and into aninternal passage 420 of the micro plunger injection assembly 404/colddeck nozzle assembly 406 in a controlled manner. A control system, 500,controls and coordinates the timing of silicone movement through thesystem 400 as is described in detail subsequently. Although pneumaticpressure is utilized to force or drive silicone from the siliconecartridge assembly 402, any other suitable means may be utilized.

The micro plunger injection assembly 404 comprises a housing 422 throughwhich a plunger rod 424 travels. This plunger rod 424 is utilized toforce the silicone through the internal passage 420 of the cold decknozzle assembly 406 based on commands by the control system 500. Theplunger rod 424 may vary in size from 0.5 mm to 6.5 mm and the internalpassage or bore 420 is sized accordingly. A plunger seal pack 426 sealsthe plunger rod 424 at the various sizes (0.5 mm to 6.5 mm). The housing422 surrounds and secures the plunger rod 424 therein. The plunger rod424 may be driven pneumatically, via an electric servo motor or anyother suitable means. In the illustrated exemplary embodiment, theplunger rod 424 is driven pneumatically via two pneumatic ports 428 and430. When port 428 is pressurized via commands from the control system500, the plunger rod 424 moves forward driving the silicone through thecold deck nozzle assembly 406 and into a mold cavity, not illustrated.This injection is timed with the operation of the cold nozzle assembly406. When port 430 is pressurized via commands from the control system500, the plunger rod 424 moves backward and silicone enters the materialchannel and is moved through the cold deck nozzle assembly 406 and thesystem 400 is recharged and ready to execute the next injection or shotof silicone to form a part. A plunger rod piston O-ring 432 ispositioned around the plunger rod 424 proximate a plunger rod indicatorflag 434. A shot adjusting knob 436 connected to a shot adjuster 438 maybe utilized to set or fine tune the size of the silicone shot to beinjected into the cavity mold. In other words, the shot adjuster 438 maybe utilized to set the number of micrograms of silicone to be ejectedfrom the cold deck nozzle assembly 406 in a single shot. The shotadjuster 438 passes through a threaded lock nut 440 mounted to thehousing 422 such that by simply turning the knob, 436 more or lesssilicone may be ejected based on the throw of the plunger rod 424. Asset forth above, the plunger rod 424 in this exemplary embodiment is 3mm in diameter and the injection stroke length is adjustable via theshot adjuster 438 and lock nut 440, both of which include fine threadsfor precise adjustment. A manifold block 442 with inside bore orinternal passage 420, in which the silicone flows to the cold nozzle448, is mounted to the end of the micro plunger injection assembly 404opposite that of the shot adjuster 438 end.

The cold deck nozzle assembly 406 is directly connected to both thesilicone cartridge assembly 402 and the micro plunger injection assembly404. The cold deck nozzle assembly 406 comprises a nozzle holding base444, a cold nozzle holding block 446 and the cold nozzle 448. The coldnozzle 448 comprises two pneumatic inlet ports 450 and 452 which controlan internal valve, described in detail subsequently, that opens andcloses the cold nozzle 448. Control signals from the controller 500 openthe nozzle 448 for delivery of a shot and close the nozzle 448 after theshot has been delivered or between shots. As before, any other suitablemeans may be utilized to open and/or close the nozzle 448. The cold decknozzle assembly 406 also comprises water circulating ports 454 whichprovide chilled water to the cold deck nozzle assembly 406 in order tomaintain the temperature of the silicone at the optimum workingtemperature. The water is utilized to maintain the silicone at atemperature range of about seventeen (17) to about twenty (20) degreesCelsius. A pressure sensor/transducer 456 is mounted in line withinternal passage 420 on the opposite side of the cold nozzle 448. As setforth above, the pressure sensor/transducer 456 is hard wired into thecontrol system 500 to control the injection sequencing and flow ofmaterial through the system 400. O-ring seals 458 a, 458 b and 458 c arepositioned around the cold nozzle 448 to prevent water from contactingthe silicone.

FIG. 5 illustrates a detailed and expanded view of the cold nozzle 448.As illustrated, the O-ring seals 458 a, 458 b and 458 c are positionedin grooves of the cold nozzle 448 to provide a sealed separation betweenthe silicone material flow and cooling water flow channels. Siliconematerial enters the cold nozzle through orifice or opening 460 locatedbetween O-rings 458 b and 458 c and flows up around the shut-off valveor pin 462. Water enters the cold nozzle 448 through a channel 464between O-rings 458 a and 458 b and flows up, around and then back downinside of the long slim portion 466 of the nozzle assembly 448. Thelarge body section 468 of the assembly comprises the nozzle shut-off pinpiston assembly that opens and closes the nozzle 448. As describedabove, pneumatic inlet ports 450 and 452 supply the air pressure to openand/or close the nozzle 448.

The exemplary micro silicone mold mounted plunger unit or system 400functions as set forth in detail below. When molding parts orcomponents, silicone from the silicone cartridge assembly 402 is driveninto the micro plunger injection assembly 404 via controlled airpressure regulated by the control unit 500. Silicone in the inside boreor internal passage 420 is driven through the cold nozzle 448 of thecold deck nozzle assembly 406 via commands from the control system 500and into the mold cavity. The control unit of system 500 is programmedto run the entire process in accordance with a preferred procedure. Thecontrol system 500 is a feedback based system that may be implemented inany suitable manner, including through the use of a micro-controller.The control unit of system 500 is programmed to run the entire processin accordance with a preferred procedure. The control system 500 is afeedback system that may be implemented in any suitable manner,including the use of a micro-controller. As set forth herein, the shotsize is determined by the stroke of the plunger rod 424 which may beadjusted manually by the shot adjuster 438, or from the controller to aservo drive. Silicone flow itself from the cold nozzle 448 is controlledvia the control system 500 through the cold nozzle valve.

Table 1 below summarizes the displacement for the system 400. As setforth, for a thirty (30) mm stroke, the silicone displacement is 0.0144cubic inches or 0.211 grams for a single shot. For a comparison, Table 1also summarizes the displacement for currently utilized 12 mm diameterreciprocating screw devices. For a thirty (30) mm stroke in thereciprocating system, the silicone displacement is 0.2069 cubic inchesor 3.3905 grams. This is 14.3 times more silicone for a single shot. Asmay be readily understood, there is significant increase in compressionof material associated with the reciprocating screw devices currentlyutilized which result in material flow variation. The reciprocatingscrew systems are independent from the silicone mold which adds materialflow distance into the system. Here the silicone must flow from thematerial inlet port on the barrel and be augured along the screw untilit is compressed ahead of the screw tip. From here the material musttravel through the machine nozzle to enter the mold and then bedistributed equally to each cavity. This entire system is subject tomaterial compressibility which equates to variation in material pressureand flow rate.

The exemplary micro silicone mold mounted plunger unit or system 400specifically reduces the flow path of silicone such that quality andreproducibility is increased while waste is reduced. In this system theinjection unit is incorporated into the silicone mold extremely close tothe cold shut-off nozzle. The system has a greatly reduced material flowchannel diameter which is held constant up to the point of exiting thecold nozzle orifice. This provides a stable pressure constant within thesystem unlike that of a reciprocating screw system that begins with a 12mm diameter material channel and then reduces over the length of theflow path of the system. The actual injection stroke end position islocated at the junction of the material flow channel and the coldshut-off nozzle. This arrangement and reduced material channel volumessignificantly reduces material compression and pressure variation in theflow of the material thereby providing superior shot to shotrepeatability.

As set forth in Table 1, the material displacement, 0.211 grams, for asingle shot is substantially equal to the desired total shot weight of0.218 grams. This is only achievable with the design set forth hereingiven the direct connections and extremely short flow paths. With themicro plunger injection assembly connected directly to the cold decknozzle assembly, the plunger rod drives the thermoset elastomer,silicone, through the internal passageway or bore of the cold decknozzle assembly and the cold deck nozzle.

TABLE 1 Material Rod/ Dis- Material Screw place- Dis- “Area” ment place-Injection (Cubic (cubic ment Type Out total shot weight is 0.218 grinches) inches) (Grams) Plunger Stroke maximum is 50 mm 0.0129 Strokeminimum is 1 mm 0.0129 Stroke used is 30 mm 0.0129 The 3 mm diameterplunger has 0.0129 an area of Displacement of 3 mm rod 0.0144 0.211 @ 30mm stroke = Displacement of 3 mm rod 0.0004 0.0066 @ 1 mm stroke =Displacement of 3 mm rod 0.0214 0.3516 @ 50 mm stroke = Recipro- A 12 mmdiameter reciprocating 0.752 cating screw has an area of ScrewDisplacement of 12 mm 0.2069 3.3905 diameter screw @ 30 mm stroke =

In a typical injection molding system, the nozzle of the injection unitinjects the molten or liquid material, for example, silicone, into amold or die. A sprue is a channel through which the molten or liquidmaterial is injected out from the nozzle of the injection unit and intothe mold. The sprue generally has a smooth, round, tapered configurationthat facilitates smooth material flow therethrough. Runners are channelsthrough which the molten material flows from the sprue and into thecavities of the mold via gates. A gate is an entrance through which themolten material enters the cavity. The gate performs a number offunctions, including restricting the flow and direction of moltenmaterial and facilitating removal of the parts from the runners.

It is important to note that while the term sprue refers to the channelor passageway through which a molten or liquid material flows into acavity or die where it solidifies or cures to form molded parts, it alsorefers to the material which solidifies or cures in the channel itself.Similarly, the runners are also both channels, typically having asmaller diameter than the sprue, through which the molten material flowsas well as the material which solidifies or cures in the channelsthemselves. The solidified sprue and runners together form a frameworkattaching the molded parts, for example, punctal plugs, together in theroughly planer arrangement. FIG. 6 illustrates a genericsprue/runner/gate/component configuration or framework 600. Asillustrated, the sprue 602 is connected to the runners 604 which areconnected to the molded parts 606 via gates 608.

The present invention is directed to precision cassette plates forsecuring any number of molded parts, for example, punctal plugs. Thecassette plates are part of the molds utilized in combination with theexemplary micro silicone mold mounted plunger injection unit which inturn is part of a small scale, self-contained, fully enclosed, filtered,manufacturing cell that molds and distributes micro-sized components,for example, punctal plugs, throughout the complete assembly process. Adetailed description of the exemplary cassette plates is givensubsequently. FIGS. 7A and 7B illustrate an exemplary cell 700. Theexemplary cell 700 comprises an injection molding unit 702, a mold standand/or base 704, a mold 706, a cassette pre-heating station 708 and arobotic manipulator 710 mounted within a case 712 having a filtrationunit 714 for maintaining a substantially particle free environmentwithin the case 712. One or more cassette holding assemblies or racks716 may be utilized to hold either cassettes with parts or fullcassettes, empty cassettes or both full cassettes and empty cassettes asis explained in detail subsequently.

The manufacturing cell 700 is preferably designed with the cassettepre-heating station 708 that is capable of pre-heating a cassette,described in detail subsequently, to mold temperature prior to placementinto the mold. The cassette is an integral part of the molding processas a single cassette is placed into the mold at the beginning of eachcycle by the robotic manipulator 710. Upon completion of the moldingcycle, the filled cassette and sprue/runner are removed from the moldand then another empty cassette is placed into the mold. During thesubsequent molding cycle, the robotic manipulator 710 discards thesprue/runner at a discard location and then positions the filledcassette at the next manufacturing stage. These cassettes are key tomanaging part handling and positioning of individual micro-sized partsthroughout the manufacturing process. For example, in creating a drugrelease system, after each punctal plug is molded, the reservoir in eachpunctal plug is filled with a drug formulation and the cassettes allowfor each plug to be managed from beginning to end of the process.

The cassettes may be reusable and manufactured from any number ofsuitable materials, including stainless steel. The cassettes may in analternate embodiment be a single use device that is fabricated from anysuitable materials such as thermoplastic resins. The cassette is alsokey to establishing a self de-gating molding process as it holds themolded part during the de-gating process. Essentially, the cassettes maybe fabricated from any suitable biocompatible material, includingceramics, polymers and metals and/or metal alloys such as cobalt alloys.

The cassettes, as described in detail below, are designed with twopre-alignment holes and two precision positive anti-rotational featuresthat guarantee accurate placement of the cassette each time at eachstage of the manufacturing process. Two pre-alignment pins engage thecassette during the closing stage of the molding process to ensure thecassette is sealed into the mold prior to the final mold clamp stage. Itis important to note that the two precision positive anti-rotationalfeatures may comprise any suitable configuration.

Referring now to FIG. 8, there is illustrated an exemplary cassette 800.The cassette 800 preferably comprises a precision thin plateconstruction with a substantially circular shape; however, other shapesmay be utilized. As set forth above, the cassette 800 may be designed tohold any number of parts, for example, punctal plugs. In the illustratedexemplary embodiment, the cassette 800 is designed to hold four partsand as such has four through-holes 802 which engage the parts as isexplained in detail subsequently. The cassette 800 also comprises twopre-alignment through-holes 804. These pre-alignment though-holes 804accept cassette alignment pins, described in detail subsequently, toensure that the cassette 800 is seated properly in the mold prior to thefinal mold clamp stage. The cassette 800 also comprises two precisionanti-rotational features 806 and 808. The features 806 and 808 maycomprise any suitable shape that prevents the cassette from rotating. Inthe illustrated exemplary embodiment, features 806 and 808 have adifferent configuration and size such that cassette 800 cannot bemisaligned. The features 806 and 808 may be positioned at any suitablelocation on the precision cassette plate 800. In the illustratedexemplary embodiment, the features 806 and 808 are cut or fabricatedalong the perimeter of the precision cassette plate 800 one hundredeighty (180) degrees apart from one another. The diameter of thecassette 800 and the thickness of the cassette may vary with design. Theprecision cassette plate 800 may be fabricated from any number ofsuitable materials. For example, the material may change depending onwhether the plate is to be reused or discarded after a single use.Exemplary materials include stainless steel and thermoplastic resins.

FIG. 9 is an exploded diagrammatic representation of the exemplary moldassembly configuration 900 in accordance with the present invention andhow the cassette 800 fits into the mold. The top portion 902 of the moldassembly comprises any suitable configuration made from any number ofsuitable materials. In the exemplary embodiment, the top portion 902 ofthe mold assembly may comprise a round or square stainless steel corepin retaining insert. The top portion 902 comprises two cassettealignment pins 904 (one of which is illustrated) which mate with the twopre-alignment through-holes 804 in the cassette 800 illustrated in FIG.8. If more pre-alignment through-holes in the cassette 800 are utilized,additional alignment pins 904 may also be utilized. The top portion 902also comprises four cavity core pins 906, one of which is illustrated.In this exemplary embodiment, four cavity core pins 906 are utilizedbecause the cavity 800 comprises four holes 802 for four parts. The fourcavity core pins 906 create cavities in the parts. For example, punctalplugs that release drugs comprise a reservoir for holding the drug andthe cavity core pins 906 form these reservoirs. Both the cassettealignment pins 904 and the cavity core pins 906 pass through thecassette 800.

The cassette 800 is seated above or on the runner/gate insert element908. As illustrated, the runner/gate insert element 908 comprises asprue channel 910 and four runner channels 912, two of which areillustrated. Since the cassette 800 is configured for four parts, fourrunner channels 912 are required. The runner/gate insert element 908 maycomprise any suitable configuration and be constructed from any suitablematerial. In the exemplary embodiment, the runner/gate insert element908 is constructed from stainless steel. The runner/gate insert element908 is positionable on the mold assembly base 914.

The mold assembly base 914 is illustrated with a sprue-runner framework916 positioned thereon. The mold assembly base 914 comprises an opening918 through which the nozzle 448 of the injection unit 400 is positionedto make fluid contact with the sprue 910. The mold assembly base 914 maycomprise any suitable configuration and be constructed from any suitablematerial. In the exemplary embodiment, the mold base assembly 904 isconstructed from stainless steel. Once all of the elements are aligned,the mold assembly is clamped together and silicone may be injected toform parts.

Although the mold assembly may comprise any number of materials, in apreferred embodiment, the components are fabricated from stainlesssteel, and more preferably, a high grade stainless steel.

Referring now to FIG. 10, there is illustrated a detailed diagrammaticrepresentation of a single runner 912, a gate 922 and the tip of a part924, for example, the tip of a punctal plug. Arrow 1000 show thedirection of material flow through the runner 912, though the gate 922and into the mold cavity to form the part of which only the tip 924 isillustrated. Essentially, the diagrammatic representation depicts thetypical material flow path when gating directly onto the tip portion ofthe part 924. The material flows vertically down into the mold throughthe sprue (not illustrated) and into the horizontal runner system whereit is then directed to the actual gate location. The gate 922 iscentered axially on the tip of the part 924 to provide a balancefill/flow of the material, and an easy break away during the demoldingor de-gating process.

The cassette is an integral part of the mold assembly configuration andthe material handling process. With this configuration, the overall sizeand complexity of the mold and molding process may be simplified. Thecassette provides for shorter runner lengths which in turn allow forbetter control over pressure variations. In addition, the cassetteallows parts to be transferred to and through the process without asecondary cutting operation. In other words, everything maintains itsorientation until the time of part separation.

As described above with respect to FIG. 8, features 806 and 808 have adifferent shape in this exemplary embodiment. The different shapes areso that there is a consistent and predictable location for each part oneach cassette 800. For example, in the illustrated exemplary embodiment,the hole 802 designated as hole 1 will comprise the same part orcomponent as the hole 802 designated as hole 1 in any cassette 800.Accordingly, these features 806 and 808 provide traceability of parts orcomponents throughout the entire process.

FIGS. 11A and 11B illustrate an exemplary cassette 800 comprising parts1100 in each of the holes 802. Once the injection process is complete,the cassette 800 with parts or components 1100 is removed from the moldassembly 900 for storage and/or further processing. In the exemplaryembodiment illustrated in FIG. 7, the cassette 800 is stored in acassette rack 716. However, in alternate exemplary embodiments, thecassette 800 with parts or components 1100 may be moved to a new stationin any ongoing process such as drug filling. Once the cassette 800 withparts 1100 is removed from the mold assembly 900, an empty cassette 800is placed therein. In the exemplary embodiment described herein, therobotic manipulator 710, illustrated in FIGS. 7A and 7B, performs theremoval and insertion of the cassettes 800.

FIG. 12 illustrates, in detail, a portion of an exemplary cassette 800in the mold assembly 900 attached to the sprue 910 and runner 912through gate 922. As illustrated, the cavity core pin 906 which projectsfrom the core pin insert 902 form the cavity in the component 924, aportion of which is shown. When the component 924 is complete, thecassette 800 with the components 924 are removed from the mold assembly900 wherein the sprue 910 and runners 912 are separated from the parts924.

The precision cassette of the present invention may be positionedanywhere in the molding process while maintaining the orientation of themolded parts or components. In addition, the precision cassette with thepats secured therein may also be utilized in further processing and/ormanufacturing steps without changing the orientation of the molded partsor components. For example, the precision cassette may be utilized tosecure the molded parts or components for coating and/or filling. Inother words, the precision cassette may be utilized to secure and alignparts for drug and/or therapeutic agent filling to create a drugdelivery medical device such as a punctal plug. With this precisioncassette, there is no need to remove the molded parts or components to asecondary device for post molding processing. The drug filling maycomprise any suitable process for adding a therapeutic agent to moldeddevice. The therapeutic agent may be in any form, including dry, liquid,and fiber.

The precision cassette may be utilized under any number processingconditions, including large temperature ranges, large pressure rangesand large humidity ranges. The precision cassette may comprise anysuitable shape and profile as well as include any number of additionalfeatures, all depending on the application. The precision cassette maybe constructed from any number of suitable materials, once againdepending on the application. Essentially, the size, shape, profile andmaterial forming the precision cassette may be tailored for particularapplications and are thus important design constraints or parameters. Inaddition, although described with respect to an injection moldingprocess, the precision cassette may be utilized in other types ofmolding processes, including compression molding, transfer molding andcasting under vacuum. Also any suitable materials may be molded in theprecision cassette. For example, silicone, thermoplastic resins andmetallic materials may be molded in the precision cassette.

The precision cassette plate as shown and described herein is a unitary,thin plate or disc; however, in alternate exemplary embodiments, theprecision cassette plate may comprise other designs such as a splitdesign structure or a split design with a hinge connection. In a splitdesign, the precision cassette plate may comprise two or more piecesdesigned to be separated for removal of the molded parts or components.In a split design with hinges, the one or more pieces may be connectedtogether with hinges, but still perform the same function. In yetanother alternate exemplary embodiment, the perimeter of the precisioncassette plate may be tapered or chamfered in order to facilitateinsertion into or removal from the mold assembly. In yet anotheralternate exemplary embodiment, the precision cassette plate may have asurface finish and/or coating thereon to facilitate placement, handlingand part or component separation.

Although shown and described is what is believed to be the mostpractical and preferred embodiments, it is apparent that departures fromspecific designs and methods described and shown will suggest themselvesto those skilled in the art and may be used without departing from thespirit and scope of the invention. The present invention is notrestricted to the particular constructions described and illustrated,but should be constructed to cohere with all modifications that may fallwithin the scope of the appended claims.

What is claimed is:
 1. A mold assembly for an injection molding system, the mold assembly comprising: a top portion, the top portion including one or more cassette alignment pins extending therefrom; a precision cassette plate, the cassette plate including one or more openings through the precision cassette plate in which parts are fabricated and secured, one or more pre-alignment through-holes which engage the one or more cassette alignment pins and configured to ensure accurate placement of the cassette, and two anti-rotational features, the precision cassette plate in combination with the two anti-rotational features is configured to hold and secure the fabricated parts formed therein in a particular orientation, the two anti-rotational features having different sizes and shapes and positioned along the perimeter of the precision cassette plate, extending through the precision cassette plate and configured to prevent rotational movement; a runner/gate insert element, the runner/gate insert element including a sprue channel and one or more runners and gates, the number of runners and gates equals the number of openings in the precision cassette plate; and a base portion, including an opening through which a nozzle of an injection molding system is positioned and makes contact with the sprue channel of the runner/gate insert element.
 2. The mold assembly for an injection molding system according to claim 1, wherein the top portion further comprises one or more cavity core pins extending therefrom for forming cavities within the parts, the number of cavity core pins equals the number of openings in the precision cassette plate.
 3. The mold assembly for an injection molding system according to claim 1, wherein the precision cassette plate is a substantially circular shaped disc.
 4. The mold assembly for an injection molding system according to claim 1, wherein the precision cassette plate comprises stainless steel.
 5. The mold assembly for an injection molding system according to claim 1, wherein the precision cassette plate comprises a metallic material.
 6. The mold assembly for an injection molding system according to claim 1, wherein the precision cassette plate comprises a metal alloy.
 7. The mold assembly for an injection molding system according to claim 1, wherein the precision cassette plate comprises a polymeric material. 